Cytocompatibility and uptake of polycations-modified halloysite clay nanotubes

© 2018 Elsevier B.V. The increasing use of clay-based polymer composite materials in industry and biomedicine stimulates the investigation of cellular uptake and toxicity of polymer\clay composites. In particular, halloysite nanotubes have become a promising material for a number of applications. Among other polymers, cationic polyelectrolytes have been employed in numerous studies as halloysite surface modifiers, without paying the proper attention to their toxicity. In this study we report our results on cytocompatibility and uptake of polycations-coated halloysite nanotubes. Adsorption of polycations onto clay nanotubes was investigated using microscopy and dynamic light scattering. We investigated cellular distribution and biological effects of halloysite surface-modified with poly(ethylenimine), poly(diallyldimethyl-ammonium) and poly (allylamine). We have employed a set of biological methods, such as microscopy (dark-field, electron and atomic force) and enzymatic tests to assay the toxicity of polycations-coated halloysite, using A549 human endothelial carcinoma cells in 2D and 3D cultures as the biological model. We found that polycations adsorbed onto halloysite surfaces significantly increase the otherwise low toxicity of pristine clay nanotubes, inducing cellular and nuclear defects.